The present invention pertains to a transmission circuit, an antenna duplexer, and a radio-frequency circuit.
Conventionally, there is proposed, as an example of a transmission line used in radio-frequency circuits, one where a meander-shaped line and a shield electrode are disposed inside a laminated substrate.
There is also proposed a delay line, comprising a spiral-shaped coil conductor and a shield electrode formed on top and bottom of the coil conductor so as to face this coil conductor through a dielectric ceramic layer, and formed with a strip line structure between the coil conductor and the shield electrode (e.g. JP-A-05-029819 (Patent Document 1)).